In various agricultural procedures it is common to modify an environment locally using structures which at least partially wall off some crop or animal from adverse effects such as sunshine, rain, hail, snow, or wind. In many cases the wall may conveniently be made of a usually porous fabric (that is, including apertures passing through the fabric) rather than a solid construction, as a suitably supported porous fabric provides sufficient modification of the adverse effect under consideration without introducing other adverse effects--such as total shading. For example, a windbreak may be made of an unrolled porous fabric supported like a fence between substantially vertical posts to windward of the objects to be protected. Alternatively perimeter walls and an overhead canopy of a more porous fabric may be provided over the entire area to be protected.
Porous fabrics constructed from the preferred polyethylene, polypropylene or polyester yarns are flexible, extensible, and liable to abrade. They are preferably given resistance to ultraviolet light. Such fabrics are usually supplied in rolls of a specified width and typically 330 or 660 feet (100 or 200 meters) in length, have selvedged edges, and are of indefinite length. They also have minimal shear strength in the plane of the fabric which results in minimal transfer of load--which may be imposed by the wind or a build-up of snow or hail--from an attachment point to adjacent yarns not directly attached. Most constructions support the loaded fabric with linkages between the selvedges of the fabric and the usual steel supporting cables under tension arranged to run parallel to and alongside the strips of fabric.
To effectively build a durable, reliable and economical structure using these fabrics, it is desirable to be able to hold them in a way that shares and transfers the load between the maximum number of yarns and each attachment point (clips, in this invention) which are linked via external support cables under significant tension to support members. At the same time, the system should be easy to install in the field.
Preferred arrangements for the spatial positioning and support of the cables are as follows: